Rotor device for an electric motor and/or generator, rotor and motor with such a rotor device as well as production method

ABSTRACT

A rotor device for an electric motor and/or generator with a rotor body and a plurality of magnets, wherein the rotor body comprises a rotor shaft seat and a plurality of magnet receptacles arranged coaxially with the rotor shaft seat. The magnets are rigidly positioned and mounted in the magnet receptacles by means of a plastic molding compound injected into the magnet receptacles, which plastic molding compound forms at least one cover element that covers the openings of the magnet receptacles at least partially. The cover element comprises at least one magnet wheel centering means and/or at least one magnet wheel alignment means. The invention furthermore relates to a rotor and a motor with such a rotor device as well as to a production method

CROSS-REFERENCE TO RELATED APPLICATIONS

The present patent application is a continuation of InternationalApplication No. PCT/DE2016/200507, filed Nov. 9, 2016, which is basedon, and claims priority from, German Application No. DE 10 2015 121102.5, filed Dec. 3, 2015, both of which are incorporated herein byreference in their entireties.

BACKGROUND OF THE INVENTION (1) Field of the Invention

The invention relates to a rotor device for an electric motor and/orgenerator. The invention furthermore relates to a rotor and a motor withsuch a rotor device as well as to a production method for such a rotordevice.

(2) Description of Related Art Including Information Disclosed Under 37CFR 1.97 and 1.98

The term “electric motor” refers to an electromagnetic transducer, whichconverts electrical energy into mechanical energy. In doing so, aphysical principle is used, wherein a current-carrying conductorgenerates a magnetic field and different magnetic fields exert forces oneach other. These forces are also called Lorentz forces. An electricmotor that can generate a rotational movement generally comprises arotatable component (also called a rotor) and a stationary or fixedcomponent (also called a stator). Here, separate magnetic fields aregenerated in each case in the rotor and in the stator, wherein themagnetic fields are generated by at least one of the components by meansof one or more current-carrying coils. There is also the possibility ofgenerating one of the magnetic fields by means of permanent magnets orfield magnets. The magnets are, for example, inserted into appropriatereceiving pockets in a rotor.

A rotor device of the type mentioned is known, for example, from DE 202012 103 438 U1. The previously known rotor device comprises a rotorcore lamination stack consisting of several rotor core laminationsconnected to each other axially, wherein the rotor core lamination stackcomprises receiving pockets in which permanent magnets are accommodated.The permanent magnets are held in the receiving pockets by a castingmaterial. The receiving pockets or the permanent magnets are covered onone side by a support ring.

In the case of brushless direct-current motors, it is necessary tocontrol the individual developments of a rotor precisely at predefinedpoints in time. For this purpose, the controller needs information aboutthe current alignment of the rotor. This typically takes place via amagnet wheel, which is mounted on the end face of the rotor. In doingso, care must be taken that the magnet wheel is precisely aligned withrespect to the rotor so that correct information about the currentposition of the rotor is transmitted to the controller. In thepreviously known rotor device according to DE 20 2012 103 438 U1,attaching and aligning a magnet wheel requires additional productionsteps, which increases the production costs of such rotor devices,especially in the case of series production.

BRIEF SUMMARY OF THE INVENTION

The aim of the invention consists in specifying an improved rotordevice, which makes it possible to simply and cost-effectively attach amagnet wheel. It is furthermore the aim of the invention to specify arotor, a motor with such a rotor device, and also a production method.

The invention is based on the idea of providing a rotor device for anelectric motor and/or generator with a rotor body and a plurality ofmagnets, wherein the rotor body comprises a rotor shaft seat and aplurality of magnet receptacles arranged coaxially with the rotor shaftseat and the magnets are arranged in the magnet receptacles. The magnetsare rigidly positioned and mounted in the rotor body, in particular inthe magnet receptacles, by means of a plastic molding compound injectedinto the magnet receptacles, wherein the plastic molding compound formsat least one cover element, which covers the openings of the magnetreceptacles at least partially. The cover element comprises at least onemagnet wheel centering means and/or at least one magnet wheel alignmentmeans.

The injected plastic results in the advantage of a cost-effective,reliable, and permanent fixing of the block magnets in the rotor corelamination stack. In the process, up to two annular end faces or coverelements can be molded on at the same time, onto which at least one ballbearing can be pressed, that is, using an interference fit. In thiscase, a molded-on cover element is formed or arranged on one end of therotor body and another optional cover element is formed or arranged onthe other, opposite end of the rotor body. Due to the magnet wheel beingmolded on, another part can be dispensed with, which supports the rotoror which withstands an interference-fit process onto the motor shaft.

The magnet wheel centering means serves to center a magnet wheel on therotor shaft. The magnet wheel centering means thus brings about acentered or coaxial alignment of the magnet wheel and avoids imbalances.The magnet wheel centering means also has a stop function, whereby agenerally known “stick-slip effect” is avoided and a more precisemounting is made possible as a result of fixing the bearing by aninterference fit.

The magnet wheel alignment means serves to align the magnet wheel inorder to provide correct commutation. In this way, an angularmisalignment of the magnetic poles occurring between the active rotormagnets and the magnet wheel, which can lead to faulty commutation, isprevented. In this case, the rotor position can be determined in manyapplications by three switching Hall sensors via the alignment of themagnet wheel.

In the prior art, the rotor magnets were often simply lengthened inorder to detect the rotor position. These lengthened magnets have thedisadvantage that they often consist of rare-earth magnet material andare thus very expensive. On the other hand, this significantly increasesthe rotor moment of inertia, whereby the accelerating and brakingability is worsened. In order to eliminate these disadvantages, the ideathus suggests itself of mounting a separate magnet wheel consisting offerrite magnets or plastic-bonded ferrite or rare-earth magnets on therotor, in particular on the cover element, using the aforementionedmeans.

In connection with the present invention, it is pointed out that theterm “rotor core lamination stack” typically refers to a rotor body witha plurality of metal disks or metal layers, which are arranged togetherand, lying on top of each other, form the rotor body. The metal disksare mostly electrically insulated from each other using lacquer orlaminate in order to suppress eddy currents arising from a changingmagnetic field and to thus reduce losses and heat produced by thecurrent.

The magnet wheel centering means is preferably integrally molded ontothe cover element as an insulating ring. The insulating ring has theadvantage that it can be easily produced at low cost. The insulatingring can in particular be integrally molded on during the formation ofthe cover element. The magnet wheel centering means is in particular aninsert molding around the rotor shaft. It has also been provenadvantageous that the insulating ring can preferably serve both asmagnet wheel centering means and as magnet wheel alignment means if, forexample, the outer surface is designed with alignment elements. This isthe case when the insulating ring is not a rotation body but hasindentations and/or edges, such as in the case of a hexagon head screw.As a result, a magnet wheel can only be mounted on the insulating ringin a certain alignment.

The magnet wheel alignment means can be integrally molded onto the coverelement as at least one pin element. A pin element can be easilyproduced at low cost and can in particular also be integrally molded onduring the formation of the cover element.

In an advantageous embodiment, the cover element has a hole congruentwith the rotor shaft seat. This results in the advantage that a sealingarises between the rotor shaft and the cover element when the rotorshaft is inserted.

It has also been proven to be advantageous when the cover element isdesigned to be disk-shaped and/or annular. As a result of the diskshape, a circular and flat plane is molded on, which does not generatean imbalance and only constitutes a slight additional weight at therotor. The annular shape has the same advantages as the disk shape andhas even less weight.

The cover element preferably comprises a toothed edge, wherein eachtooth of the toothed edge is arranged in each case between two magnetreceptacles. As a result of the teeth, there is good contact between thecover element and the plastic molding compound injected into the rotor.The mounting of the cover element on the rotor as well as that of theinjected plastic molding compound is thus reinforced and improved.Plastic molding compound and thus weight and costs can additionally besaved because of the cavities, recesses or indentations formed betweenthe teeth.

The rotor body is preferably designed in one or more parts, inparticular as a rotor core lamination stack, wherein the magnetreceptacles fully accommodate the magnets. Iron cores made of solidmaterial as rotor bodies may be less costly but, in generators andmachines, in particular in transformers, have the disadvantage that eddycurrents arise under the influence of changing magnetic fields. Theseinduced eddy currents result in losses and heat the core with increasingfrequency. A multi-part iron core, in particular a laminated core, e.g.for a rotor body, avoids this problem since the parts or laminations areelectrically insulated from each other by means of a lacquer or laminateand since no or only minor eddy currents can thus form. As a result ofthe magnets being fully accommodated in the receptacles, a compact rotorresults, in which the magnets are better fixed and mounted by theinjected plastic.

Together with a rotor shaft mounted in the rotor shaft seat and a magnetwheel connected to the cover element, the rotor device according to theinvention forms a rotor. The present invention also relates to a motorwith a rotor device according to the invention, in particular with anaforementioned rotor.

The production method according to the invention for a rotor device, inparticular a rotor device according to the invention, was developed toachieve the aforementioned aim and comprises the following steps:

-   -   a) Providing a rotor body with a rotor shaft seat and a        plurality of magnet receptacles;    -   b) Inserting magnets into the magnet receptacles; and    -   c) Injecting a plastic molding compound into the magnet        receptacles until a cover element is formed that at least        partially covers the openings of the magnet receptacles.

This method has the advantage that the method steps can be implementedeasily and thus on a large scale in factories. The fixing and mountingof the magnets in the receptacles by means of the plastic is moreovercost-effective and can be performed quickly.

When injecting a plastic molding compound, the magnets are preferablyinsert-molded such that the magnets are fixed within the magnetreceptacles. In doing so, it is preferably kept in mind that the magnetsshould not have any play in the receptacles nor be able to get loose orfall out of them. In this way, the magnets can be insert-molded eitherpartially or completely. In the case of a partial insert molding, onlythe lateral surfaces of the magnets, can, for example, come into contactwith the plastic in particular in sections, while the upper and/or lowersides of the magnets are/is completely or partially uncovered. Themagnets or the end faces of the rotor are therefore partially uncoveredand form corresponding indentations or edges, since these sub-areas arecovered by mold parts during injection of the plastic.

In another advantageous embodiment, the inserted magnets are positioned,in particular by means of an injection-molding tool and/or an injectionmold, in the magnet receptacles before and/or during injection of aplastic molding compound. The injected plastic can in some circumstancesinfluence the alignment or position of the magnets in the receptaclesand tilt the receptacles with respect to the rotor axis, for example.The pre-positioning ensures that the magnets are correctly aligned andfixed in a certain position by means of the plastic. The magnetic orrotating field generated by the magnets is thus formed evenly anduniformly with the exception of its alternating polarity.

It is also advantageous when a magnet wheel centering means and/or amagnet wheel alignment means is preferably molded onto the coverelement. A magnet wheel is moreover preferably placed, centered, and/orpositioned on the magnet wheel centering means and/or on the magnetwheel alignment means. The magnet wheel is also preferably connected tothe magnet wheel centering means and/or the magnet wheel alignment meansby ultrasonic welding, hot pressing, and/or gluing.

In another advantageous embodiment, the magnet wheel is directlyinjected onto the cover element by means of a two-componentinjection-molding process. As a result, the rotor can be processedfurther immediately after the formation of the cover element, withouttaking the rotor out of the injection-molding line. This saves time andcosts during the production process.

The injected plastic molding compound in the rotor device according tothe invention and in the production method according to the inventioncan advantageously consist of, contain, or be produced from one or moredifferent liquid-crystal polymers (LCP). In particular as a result ofthe strongly anisotropic geometry of the LCPs, a strong intermolecularcohesion arises, whereby high melting points are achieved.

In the production of the rotor device, the rotor shaft can be insertedinto the rotor body before or after fixing the magnets in thereceptacles by means of the plastic and forming the cover element.

The invention, in particular the rotor device according to the inventionand the method according to the invention, are suitable in particularfor application in BLDC motors, i.e. in brushless direct-current motors.The invention is in particular suitable for application in brushlessdirect-current motors that are used for driving pumps in oil productionbut also for pumping other viscous media. A particularly advantageousapplication results for brushless direct-current motors in oil pumps ofmotor vehicles.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The invention is described below with reference to exemplaryembodiments, which are explained in more detail with reference to thefigures. They show:

FIG. 1 is a perspective view of a rotor body of the rotor deviceaccording to the invention according to a preferred exemplary embodimentwith inserted magnets and rotor shaft;

FIG. 2 is a rotor device according to the invention according to apreferred exemplary embodiment with the rotor body according to FIG. 1;

FIG. 3 is the rotor device of FIG. 2 with magnet wheel centering meansand magnet wheel alignment means;

FIG. 4 is a rotor with the rotor device according to the invention fromFIG. 3;

FIG. 5a is another perspective view of the rotor of FIG. 4;

FIG. 5b is the rotor of FIG. 5a , with a magnet wheel placed and mountedon it;

FIG. 6 is an arrangement of a rotor of FIG. 5b in a rotor bearingholder, in particular in a circuit board with Hall sensors;

FIG. 7 is a cross-section of a BLDC motor with the arrangement of FIG. 6and a stator;

FIG. 8a is a rotor device according to the invention according to apreferred exemplary embodiment with a rotor shaft and a circular designof cover element;

FIG. 8b is the rotor device of FIG. 8a with a magnet wheel placed on it;

FIG. 9a is a rotor according to the invention according to a preferredexemplary embodiment with a ball bearing placed on it; and

FIG. 9b is a side view of the rotor of FIG. 9 a.

DETAILED DESCRIPTION OF THE INVENTION

In describing preferred embodiments of the present invention illustratedin the drawings, specific terminology is employed for the sake ofclarity. However, the invention is not intended to be limited to thespecific terminology so selected, and it is to be understood that eachspecific element includes all technical equivalents that operate in asimilar manner to accomplish a similar purpose.

FIG. 1 shows a perspective view of a cylindrical rotor body 2 comprisingseveral disks with six magnets 3 inserted into the magnet receptacles 5and a rotor shaft 15 inserted into a rotor shaft seat 4. In addition,six holes 18 are formed concentrically about the rotor shaft seat 4 andextend, like the rotor shaft seat 4 and the magnet receptacles 5, fromthe top end face to the bottom end face of the rotor body 2. The rotorbody 2 comprises three planes of symmetry, wherein the commonintersecting line of all three planes constitutes a rotor shaft axis.The rotor shaft axis extends centrally in the rotor shaft 15 andconstitutes its axis of symmetry or axis of rotation. Each plane ofsymmetry has an angle of 60° with respect to the adjacent plane ofsymmetry and extends centrally through two opposite holes 18. Themagnets 3 have the shape of a block and have a rectangularcross-section. At the edge of the rotor body 2, the six magnetreceptacles 5 substantially form circular sectors with an angle of atmost 60°, wherein each sector is delimited by an imaginary chord.Adjacent magnet receptacles 5 are in each case demarcated from eachother by a wall 17. A hole 18 is in each case arranged between a magnetreceptacle 5 and the rotor shaft seat 4. The holes 18 serve as adjustingand receiving means for an injection-molding tool in order for theplastic to be correctly injected into and onto the rotor body 2.

FIG. 2 shows the rotor body 2 of FIG. 1 with an additionally formedcover element 7, in particular as rotor device 1 according to theinvention with rotor shaft 15. The cover element 7 is formed in theshape of a disk on the top end face of the rotor body 2 and has, likethe rotor body 2, the same three axes or planes of symmetry. Three holes21 are formed on the cover element 7 concentrically about the rotor axisat a 120° angle to each other and congruently with the three holes ofthe rotor body 2. The cover element 7 additionally comprises a toothededge 10 with six teeth 11 and six indentations 19, wherein the teeth 11are arranged directly above the intermediate walls (17, not visible) ofthe magnet receptacles 5 and extend to the edge of the rotor body 2. Theindentations 19 are in each case formed in the shape of semicirclesbetween two teeth 11, in particular such that a part of the top end faceof a magnet 3 is visible. On the bottom end face of the rotor device 1,another cover element 20 is arranged, which is formed from plastic likethe first cover element 7 but does not have a toothed edge.

FIG. 3 shows the rotor device 1 of FIG. 2 with an additionally molded-onmagnet wheel centering means in the form of an insulating ring 12 and amagnet wheel alignment means in the form of three pin elements 13. Thepins 13 have the shape of bolts or cylinders and are arrangedconcentrically about the rotor axis mutually offset at an angle of 120°.The lower cover element 20 has a toothed edge that is congruent with theedge 10 of the upper cover element 7.

FIG. 4 shows the rotor device 1 of FIG. 3 with a round magnet wheel 16placed on it, in particular as rotor 14 according to the invention. Themagnet wheel 16 has the shape of a disk or ring and the same diameter asthe rotor body 2. The magnet wheel additionally has a hole or cut-outwhich is formed in the center of the magnet wheel and into which therotor shaft 15 is inserted with the insulating ring 12 in order tocenter the magnet wheel. In the magnet wheel, three holes 22 aremoreover formed, into which all three pin elements 13 are inserted inorder to align the magnet wheel.

FIG. 5a shows another perspective view of the rotor 14 of FIG. 4. Theinsulating ring 12 and the pin elements 13 have a height that is greaterthan the thickness of the magnet wheel 16.

FIG. 5b shows the rotor 14 of FIG. 5a , wherein the magnet wheel that isplaced on it is mounted by reshaped pin elements 13. The reshaping ofthe pin elements 13 is carried out by ultrasonic welding or hotpressing. In the process, the pin elements 13 lose their original heightand, similarly to a rivet, form a head that mounts the magnet wheel 16to the rotor device, in particular to the cover element 7 (notcompletely visible).

FIG. 6 shows an arrangement of a rotor 14 of FIG. 5b in a rotor bearingholder 23, in particular in a circuit board or an electronic measurementsystem 25 with Hall sensors 26. The rotor 14 is rotatably mounted in theholder 23. On the upper side of the holder 23, electrical connectors 24are arranged in order to receive one or more control signals and to sendone or more measurement signals. On the bottom end face of the holder23, the circuit board 25 is formed as a ring segment and arranged aroundthe magnet wheel 16. The three Hall sensors 26 are arranged at a 60°angle to each other concentrically about the rotor axis. The twelveelectrical contacts 30 arranged concentrically on the edge of the bottomend face of the holder 23 serve to supply current to the electric coilsof the stator described below.

FIG. 7 shows a cross-section of a BLDC electric motor with thearrangement of FIG. 6 and a stator 27. The stator is mounted on theholder 23 and comprises a certain number of coils, which generate amagnetic or rotating field in order to cause the rotor 14, in particularthe rotor device, to rotate. The rotor 14, in particular the rotor shaft15, is mounted rotatably on the holder 23 by means of a ball bearing 28,wherein the ball bearing comprises a plurality of balls 29. The injectedplastic molding compound, which forms the cover element 7 among otherthings, extends into a hole of the rotor body 2, and is lacking in theopposite hole 18, as can be seen well. The magnet wheel 16 is located ata distance from the holder 23 in order to prevent friction.

FIG. 8a shows a rotor device 1 according to the invention with a rotorshaft 15 and a cover element 7 of circular design, which is designedwithout a toothed edge in comparison to the cover element of FIG. 2.Otherwise, the cover elements 7 of FIG. 8a and FIG. 2 are identical. Theplastic molding compound 6 which is injected into the magnet receptacles5 and arranged between each wall 17 and each magnet 3 can be seen well.In this case, the plastic molding compound 6 is formed integrally withthe cover element 7. The diameter of the cover element 7 is designedsuch that the magnets 3 are partially covered.

FIG. 8b shows the rotor device 14 of FIG. 8a with a magnet wheel 16placed on it, wherein the pin elements 13 of the cover element 7 areinserted into the holes 22 in the magnet wheel 16 but have not yet beenreshaped.

FIG. 9a shows a rotor 14 according to the invention according to FIG. 5bwith a ball bearing 28 placed on the rotor shaft 15. The diameter of theball bearing 28 is smaller than the diameter of the magnet wheel 16 orof the rotor body 2.

FIG. 9b shows a side view of the rotor 14 of FIG. 9a . The pin elements13, which were reshaped as soon as the ball bearing 28 was placed ontothe shaft 15, can be seen well. The ball bearing 28 is moreover locatedat a distance from the magnet wheel 16 in order to allow the rotordevice to rotate freely.

Modifications and variations of the above-described embodiments of thepresent invention are possible, as appreciated by those skilled in theart in light of the above teachings. It is therefore to be understoodthat, within the scope of the appended claims and their equivalents, theinvention may be practiced otherwise than as specifically described.

LIST OF REFERENCE SYMBOLS

-   1 Rotor device-   2 Rotor body-   3 Magnet-   4 Rotor shaft seat (of the rotor body)-   5 Magnet receptacle (of the rotor body)-   6 Plastic molding compound-   7 Cover element-   8 Opening (of the magnet receptacle)-   9 Hole (in the cover element)-   10 Toothed edge (of the cover element)-   11 Tooth (of the toothed edge)-   12 Insulating ring (as magnet wheel centering means)-   13 Pin element (as magnet wheel alignment means)-   14 Rotor-   15 Rotor shaft-   16 Magnet wheel-   17 Wall (of the magnet receptacle)-   18 Hole (in the rotor body)-   19 Indentation/recess (of the toothed edge)-   20 Additional cover element-   21 Hole (in the cover element)-   22 Hole (in the magnet wheel)-   23 Rotor bearing holder-   24 Electrical connectors (of the rotor bearing holder)-   25 Electronic measuring system-   26 Hall sensor-   27 Stator-   28 Ball bearing-   29 Ball (of the ball bearing)-   30 Electrical contact

What is claimed is:
 1. A rotor device for an electric motor and/orgenerator, the rotor device comprising: a rotor body that has a rotorshaft seat and a plurality of magnet receptacles having openingsarranged coaxially with the rotor shaft seat; and a plurality ofmagnets, rigidly positioned and mounted in the magnet receptacles bymeans of a plastic molding compound injected into the magnetreceptacles, which plastic molding compound forms at least one coverelement, which covers the openings of the magnet receptacles at leastpartially, wherein the cover element comprises at least one magnet wheelcentering means and/or at least one magnet wheel alignment means.
 2. Therotor device according to claim 1, wherein the magnet wheel centeringmeans is integrally molded onto the cover element as an insulating ring.3. The rotor device according to claim 1, wherein the magnet wheelalignment means is integrally molded onto the cover element as at leastone pin element.
 4. The rotor device according to claim 1, wherein thecover element comprises a hole congruent with the rotor shaft seat. 5.The rotor device according to claim 1, wherein the cover element isdisk-shaped and/or annular.
 6. The rotor device according to claim 1,wherein the cover element comprises a toothed edge, with each tooth ofthe toothed edge being arranged in each case between two of the magnetreceptacles.
 7. The rotor device according to claim 1, wherein the rotorbody is in at least one part as a laminated core, with the magnetreceptacles fully accommodating the magnets.
 8. The rotor deviceaccording to claim 1, wherein the plastic molding compound comprises aliquid-crystal polymer.
 9. A motor with a rotor device according toclaim 1, further comprising a rotor shaft mounted in the rotor shaftseat, and with a magnet wheel connected to the cover element.
 10. Amethod for producing a rotor device, the method comprising the steps of:a) providing a rotor body with a rotor shaft seat and a plurality ofmagnet receptacles each having an opening; b) inserting magnets into themagnet receptacles; and c) injecting a plastic molding compound into themagnet receptacles until a cover element is formed that at leastpartially covers the openings of the magnet receptacles.
 11. The methodaccording to claim 10, wherein during injecting of the plastic moldingcompound, the magnets are insert-molded such that the magnets are fixedwithin the magnet receptacles.
 12. The method according to claim 10,wherein the inserted magnets are positioned by means of aninjection-molding tool and/or an injection mold, in the magnetreceptacles before and/or during injection of the plastic moldingcompound.
 13. The method according to claim 10, further comprising thestep of molding a magnet wheel centering means onto the cover element.14. The method according to claim 13, further comprising the step ofpositioning a magnet wheel on the magnet wheel centering means.
 15. Themethod according to claim 14, wherein the magnet wheel is connected tothe magnet wheel centering means and/or the magnet wheel alignment meansby ultrasonic welding, hot pressing, and/or gluing.
 16. The methodaccording to claim 13, wherein the magnet wheel is directly injectedonto the cover element by means of a two-component injection-moldingprocess.
 17. The method according to claim 11, wherein the moldingcompound is a liquid-crystal polymer.
 18. The method according to claim10, further comprising the step of molding a magnet wheel alignmentmeans onto the cover element.
 19. The method according to claim 18,further comprising the step of positioning a magnet wheel on the magnetwheel alignment means.